Electronic music systems of the keyboard-type heretofore constructed have been primarily of the analog type in that most of the signals to be processed are analog signals. As a result it has been difficult to provide for the programming of certain operations such as the operation of the envelope generators.
Accordingly, it is an object of the present invention to provide an improved electronic musical system that is under digital control by means of a voice code that controls many variables and interconnections associated with the system. Regarding the envelope generators, for example, in the present invention memory means, preferably in the form of read only memories, are associated with the generators for controlling such variables as envelope wave-form attack and decay. The attack time constant, for example, is varied in dependence upon the selected voice code which in turn usually corresponds to the desired instrument voice.
Another object of this invention is to provide digital keyboard circuitry that is compatible with the digital voice code control of the system and that is characterized by a sequential interrogation scheme for determining which key is being played which is in turn represented by a predetermined key and octave code.
A further object of this invention is to provide improved keyboard circuitry for generating a key and octave code and which is readily adaptable for use in a polyphonic musical system.
Still another object of this invention is to provide an improved audio waveform generator comprising a digital controlled oscillator having components thereof that are required to operate only over a one octave range thereby providing improved operation consistent with the ability to apply variable portamento or glissento across several octaves (three octaves in illustrated case).